This disclosure relates to a fuel vapor processing apparatus.
Japanese Laid-Open Patent Publication No. 2015-102020 discloses a fuel vapor processing apparatus having an adsorbent canister capable of adsorbing fuel vapor. In the fuel vapor processing apparatus, the fuel vapor vaporized in a fuel tank is introduced into the adsorbent canister and is adsorbed therein. Then, the fuel vapor is purged from the adsorbent canister and is supplied to an internal combustion engine (also, referred to as engine) during a purge operation. The fuel vapor processing apparatus further includes a flow control valve in a vapor path connecting the fuel tank to the adsorbent canister. The flow control valve is usually closed and is opened as necessary for controlling a fluid communication through the vapor path.
When the purge operation is performed, the fuel vapor adsorbed in the adsorbent canister is purged and is supplied to the engine. The fuel vapor supplied to the engine may affect an air-fuel ratio in the engine, so a correction of the air-fuel ratio in the engine is performed during the purge operation.
However, when the flow control valve is opened, the fuel vapor flows through the vapor path from the fuel tank toward the adsorbent canister depending on a difference between a pressure in the fuel tank and that in the adsorbent canister. Such flow of the fuel vapor may affect the corrected air-fuel ratio. Accordingly, there has been a need for improved fuel vapor processing apparatuses.